Vibrating apparatus have previously found utility in material transportation and manipulation applications. For example, vibratory devices have been used in material feeder, fuel rod loading, other material conveyance and material separation applications. A variety of such devices has been developed. These devices generally employ vibrational energy aligned at an angle to the direction of action of gravity to transport part along a horizontal path. Many such devices require a large number of moving parts to generate vibratory movement or specialized control mechanisms to insure that an appropriate vibrating frequency is maintained.
One vibratory apparatus design is embodied in U.S. Pat. No. 3,786,912 issued to Taylor. This vibratory apparatus features two driven masses, an action mass and a reaction mass, configured to have coincident centers of gravity. In this design, vibration is achieved by driving the two masses in an offset manner. U.S. Pat. No. 3,322,260 issued to Schwenzfeier also discusses a two driven mass system, a vibrating head and a drive head. The primary drawback of these designs is that movement of the parts is unidirectional.
U.S. Pat. No. 4,764,695 issued to Inoue et al. is directed to devices that employ a single driven mass. Specifically, the Inoue et al. device includes a vibrating member capable of orbital movement about a vertical axis without substantial rotational movement; a multi-leaf spring support means configured to form a vibration system having a substantially fixed spring constant in all directions in the plane of vibration of the vibrating member; and at least three armatures disposed around the vertical axis and confronted by electromagnets driven by multiphase a.c. current. At least three drive units are required to implement this design. One constraint of this design is that transport of parts is directed radially outwardly due to the conical shape of dispersion table 17. Moreover, actual transport of parts is driven exclusively by gravity, since the vibration serves only to minimize friction between the parts and the dispersion table.
Other prior art devices using vibrational technology in material movement or manipulation employ complex control mechanisms to achieve the desired vibrational characteristics. For example, U.S. Pat. No. 4,811,835 issued to Bullivant et al. involves vibratory material feeders characterized by controlled vibrational movement. The Bullivant et al. device includes a drive means for applying a substantially sinusoidal electrical drive wave to a vibrating mechanism (an electromagnetic vibratory actuator means); control of the frequency of the drive wave form to drive the actuator in mechanical resonance; and control of the amplitude of the drive wave form to discharge materials at a desired rate.
U.S. Pat. No. 4,921,090 issued to Gregor discloses vibratory material conveyors, characterized by specific control features. The controls of the Gregor apparatus include means for periodically turning the alternating current power supply to an electromagnetic driving means on and off; and user control means for setting the duration for timed alternating current bursts and for tuning the electromagnetic driving means at or near the natural harmonic frequency of the vibrating conveyor.
U.S. Pat. No. 4,331,263 issued to Brown discusses a vibratory feeder system with a control mechanism capable of generating vibratory movement having a predetermined amplitude and/or corresponding to the mechanical resonant frequency of the feeder. This control mechanism includes a means for sensing the third harmonic of the drive current signal in the electromagnetic driver; and/or amplitude control means responsive to the third harmonic for determining whether the amplitude of the vibrating feeder corresponds to a predetermined amplitude; and/or frequency control means responsive to the third harmonic for determining whether the frequency corresponds to the mechanical resonant frequency of the feeder.
U.S. Pat. No. 4,395,665 issued to Buchas discusses a control mechanism for vibrating a member at its resonant frequency. The Buchas control mechanism includes a vibratory movement detection means capable of producing a signal having the resonant frequency of the member; a means responsive to the detection means to induce the driver to vibrate the member at its resonant frequency. Such control mechanisms contribute to the complexity of the vibratory transport devices employing them. Again, this prior art device is capable of unidirectional part transport only.
When orientation as well as transportation of materials is desired, prior art devices employing vibrational energy aligned at an angle to the direction of action of gravity are limited to orienting parts along the transport plane. A typical application of such a vibrational transport and orientation system is to present one or more parts for subsequent processing in a standard horizontal orientation. This design therefore limits the subsequent processing that may be conducted in conjunction with these vibratory transportation/orientation devices. This prior art system features unidirectional part transport
A different system has been used when part orientation is additionally required prior to transfer from the transport plane. A plate loader manufactured by Palomar Systems and Machines, Inc. (Escondido, Calif.), for example, employs vibrational energy to randomize the motion of parts, so that they are suitably oriented and fall through sized orifices into a receiving plate. Transportation of the parts across the plate is assisted by a human or robotic operator that rotates the assembly about the horizontal plane, allowing gravity to transport the parts across the face of the plate. A vacuum may also be drawn below the receiving plate to facilitate orientation of the parts. This system is described, for example, in U.S. Pat. No. 4,395,184. Although this system is generally satisfactory, human operator assistance increases the labor required to operate the device. Moreover, a human operator may damage delicate electronic components by rotating or otherwise handling the receiving plate and reservoir containing the components too aggressively.